The present invention relates generally to propellant injectors for rocket engines and more particularly to a propellant injector which injects propellant in a series of swirled, impinging sheet layers.
Discussion
Thrust chambers for liquid propelled rocket engines include three principal components: the combustion chamber where rapid high-temperature combustion takes place; the converging/diverging nozzle where the hot reaction gasses are accelerated to supersonic velocities; and an injector which contains a plurality of injection elements to meter the flow of the propellants at a predetermined rate to achieve a predetermined fuel-to-oxidizer mixture ratio. Injectors are also operable for atomizing and mixing the fuel and oxidizer in the combustion chamber so that combustion will take place in an efficient, stable and homogeneous manner.
Conventional injectors for liquid propellants usually contain a propellant manifold and an injector plate. Injectors having this configuration typically rely on a plurality of small diameter, close tolerance orifices to control the metering, atomizing and mixing of the fuel. While construction of injectors in this manner can provide highly efficient performance, several drawbacks remain.
One drawback in particular relates to the complexity and cost of these injectors. Each of the orifices in these injectors must be precisely controlled to achieve impingement for atomization and mixing. Due to their tight tolerances and small diameter, the holes are also frequently difficult to accurately machine and gage, especially when there many elements are incorporated into the injector plate. Furthermore, the rate with which the injector plate may be machined is typically slow relative to other machining operations due to the high number and precise location of the orifices and the type of material from which the injector plate is fabricated. Lastly, errors in the machining process, such as those associated with an effect known as xe2x80x9cwanderingxe2x80x9d which can occur during the machining of small diameter holes, edge breaks, tooling failures, etc. increase the risk of scrap or the need for rework which must be factored into the cost of the injector plate. As typical injector plates have many of these orifices, frequently in excess of one hundred holes, the manufacture of these injector plates can be extremely costly.
It is one object of the present invention to provide an injector that injects a liquid oxidizer into a combustion chamber in a plurality of sheets which impinge upon each other to cause the liquid oxidizer to atomize and lose momentum.
It is another object of the present invention to provide an injector that injects a liquid fuel into a combustion chamber in a sheet which impinges upon a stream or sheet of atomized oxidizer to atomize the liquid fuel and mix the fuel and oxidizer.
It is yet another object of the present invention to provide an injector that swirls a liquid oxidizer as it is injected into a combustion chamber to promote the atomization of the liquid oxidizer and increase dwell time in the combustion chamber to improve combustion efficiency.
It is another object of the present invention to provide an injector that swirls a liquid fuel as it is injected into a combustion chamber to promote the atomization and dwell of the liquid fuel.
It is still another object of the present invention to provide an injector that employs a liquid oxidizer to form a thermal barrier at a face of the injector to protect the injector against the heat generated by the combustion of a fuel.
It is yet another object of the present invention to provide an injector that employs a liquid fuel to form a thermal shield of coolant on the combustion chamber wall to prevent hot gases from eroding, melting or otherwise damaging the chamber wall.
It is still another object of the present invention to provide a method for injecting a liquid oxidizer and a liquid fuel into a combustion chamber that utilizes multiple impingement points.
In one preferred form, the present invention provides an injector for injecting a first liquid propellant and a second liquid propellant into a combustion chamber of a rocket engine. The injector includes a first injection element for injecting a first portion of the first liquid propellant into the combustion chamber such that the first portion of the first liquid propellant enters the combustion chamber in a first sheet. A second injection element is spaced radially outward from the first injection element and injects a second portion of the first liquid propellant into the combustion chamber such that the second portion of the first liquid propellant enters the combustion chamber in a second sheet. The first and second sheets collide, causing the first and second portions of the first liquid propellant to at least partially atomize. A third injection element is spaced radially outward from the second injection element and injects at least a first portion of the second liquid propellant into the combustion chamber such that the first portion of the second liquid propellant enters the combustion chamber in a third sheet. The third sheet is collided with the at least partially atomized first propellant and produces a mixture of an atomized fuel and oxidizer. A method for injecting liquid oxidizer and liquid fuel into a combustion chamber that utilizes multiple impingement points is also provided.